Device for evaporation of liquids

ABSTRACT

A device for evaporation of liquids comprising evaporation units coupled in series. The evaporator units include a tube heat exchanger and a separating device coupled thereto. The heat exchangers are arranged aligned above each other whereby each heat exchanger forms a preseparator for the liquid to be evaporated in that heat exchanger and a subsequent separator for the steam evaporated in the preceding heat exchanger.

United States Patent [191 Riinnholm I DEVICE FOR EVAPORATION OF LIQUIDSv [75] Inventor: Arvi Riinnholm, Pori, Finland [73] Assignee: 0y W.Rosenlew AB Metallindustrin, Pori, Finland [22] Filed: Dec. 2, 1971 [21]Appl. No.: 204,079

[30] Foreign Application Priority Data Dec. 14.1970 Switzerland..l6912/70 [52] US. Cl. 159718, 202/174 [51] Int. Cl B0ld l/26 [58]Field of Search 159/18 [56] References Cited UNITED STATES PATENTS2,435.424 2/l948 Crews 159/18 3,303,l06 2/1967 Standiford,.lr. 159/183,487,873 l/l970 Bromley et al. 159/18 FOREIGN PATENTS OR APPLICATIONS576,838 5/1924 France 159/18 June 28, 1974 1,161,852 l/l964 Germanyl59/l8 Primary Examiner-Norman Yudkoff Attorney, Agent, or FirmFleit,Gipple & Jacobson [5 7 ABSTRACT A device for evaporation of liquidscomprising evaporation units coupled in series. The evaporator unitsinclude a tube heat exchanger and a separating device coupled thereto.The heat exchangers are arranged aligned above each other whereby eachheat exchanger forms a preseparator for the liquid to be evaporated inthat heat exchanger and a subsequent separator for the steam evaporatedin the preceding heat exchanger.

14 Claims, 7 Drawing Figures E I NIEB W $820582 SHEET 1 BF 7 12 COVERLIQUID 2 I DISTRIBUTOR-26 12-COVER 1 LIQUID 27a DISTRIBUTOR 12COVER 13bFILM \STEAM 14b CYCLONE 1a 40 12-COVER 42 LIQUID DISTRIBUTOR 48 STEAMCYCLON FEED PATENTEDJUHBWH Y 3.820.582

SHEET 8 OF 7 STEAM CYCLONE LIQUID DISTRIBUTOR- STEAM CYCLONE DEVICE FOREVAPORATION F LIQUIDS The present invention relates to a'device forevaporation of liquids, consisting of a number of evaporator unitsconnectedin series and of separation devices coupled to them.

Evaporation devices of this type are used, for exam-' I ple, incellulose industry for evaporation of the waste vices into the desiredsequence and in series.

Thisis why it is desirable that the space requirement of an industrialplant could be reduced with unreduced capacity or that the capacitycould be increased and the space requirement nevertheless reduced; Thepurpose of the present invention is to present a device for solving thisproblem.

The device according to'the invention is mainly char acterized by thespecial features indicated in claim 1.

The invention will be described more closely below under reference tothe attached drawings, which give schematic views of differentembodiments of the inventron. a

FIG. 1 showsa vertical section of a three-stage liquid evaporationdevice for a cellulose plant.

FIG. 2 similarly shows another embodiment of the invention. I

FIG. 3 shows onv a larger scale a vertical section of a subsequentseparator, included in FIGS. 1, 2 and 5, for liquid-containing steam asfitted with an afterseparating drop separator.

FIG. 4 shows a subsequent separator of FIG. 3 as fitted with'a differentembodiment of an after-separating drop separator.

FIG. 5 shows another embodiment according to FIG.

FIG. 6 shows a vertical section of another embodiment in whichthe steamdistributing section has been somewhat modified.

FIG. 7 shows a vertical section of another embodiment of the presentinvention.

' In FIG. 1 L 1, L-2, and L-3 illustrate vertical tube heat exchangersbelonging to the different stages in a three-stage evaporator unit. Theheat exchangers are bound together by a cylindrical jacket 1 whichlimits the tube groups and whose top end is fitted with an end cap 2 andbottom end with an end cap 3. Inside the jacket pairs of tube plates,4-5, 6-7 and 8-9 have been arranged, towhich a number of tubes have beenfastened so that they form separate heat exchangers L-l, L2 and L3 andthat after the bottom tube plates 5, 7 and 9 of the heat exchangerspre-separating spaces E-l, E-2 and E-3 are formed. Among these theheight of the pre-separating space E-2 between the tube plates 7 and 8is at least equal to the length of the tubes 10 that are used in theheat exchangers in order that tubes that must be replaced or new tubesthat must be installed can be installed into the heat exchangers L-2 andIJ-3 and inserted into the separating space E -2 through an opening 11with a cover in its wall, whereas the tubes. are inserted into the heatexchanger L-l through the removable end cap 2 at the top end of theexchanger.

The tubes can also be replaced to the various heat exchangers throughopenings 12 in line with each other in the tube plates, fitted withcovers, and through the end cap 2. In an evaporator set with severalstages it is hereby, however, required that the height of every otherseparating space is equal to the length of the tubes.

The top sections of the heat exchangers are enclosed by steamdistributor jackets 13a and 13b, of which the IS jacket 13b in the heatexchangers L-2 and L-3, to-

gether with section 14b of jacket 1, the top section of which is fittedwith an opening and which is located inside the steam distributor jacketl3b, forms a subsequent separator cyclone for steam. The steamdistributor jacket 13a in the heat exchanger L-l similarly, to-

gether with section 14a, forms a normal steam distributor into which theprimary steam is fed through a pipe 31. To the steam distributor jacket13b of each heat exchanger, L-2 and L3 a steam pipe 15a and 15b startingout from the separating space 5-1 and E-2 of the respective precedingstage is connected and a liquid pipe 16a and 16b, fitted with a throttlemeans 17, goes from the bottom edge of the steam distributor jacket tothe separating space of the respective same stage.

The jacket section 14b in the'subsequent separator cyclones of the heatexchangers 11"2 and L-3 is below the inlet of the steam pipe fitted witha hole 18, shown more closely in FIGS. 3 and 4, for regulating the upperlimit of the liquid level so that steam surges against the tube platecan in no case be produced but the liquid passes in such a case past thesteam plane directly to the condensation side. Moreover, the subsequentseparator cyclones are, according to FIG. 3 or 4 fitted with a dropseparator l9, which may be of a known type, for example, a Meshdemister.

Each heat exchanger L-3, L-2, L-l is fitted with a separate interiorheat exchanger 20, 21 and 22, which constitutes a part of the tube groupof the said heat exchanger. These are connected by means of the pipes 23and 24 through the separating spaces E-2 and E-l.

The feed liquid is pumped by means of a pump 25 through a pipe 25a andthrough the heat exchangers 20, 21 and 22 to the top end of the heatexchanger L-l into the space limited by the end cap 2.

Each evaporating tube 10 of each heat exchanger L-l, L-2, L-3 is at itstop end fitted with some known liquid distributor device 26 which guidesthe liquid to each tube so as to form a film on its inner surface. Thedistributor device is dimensioned so that it corresponds to the pressuredifference between the different stages. Underneath the tube plate atthe bottom end of each heat exchanger unit L-l, L-Z, L-3 in theseparating space E-l, E-2 and E-3 there is a conical plate system 27aarranged, in which the lower cone is fitted with holes along its lowersphere, against which the hot liquid-steam mixture streaming out of .thetubes 10 is tossed when the liquid is separated from the steam. Theliquid runs to the heat exchanger tube system of the following stage bymeans of the liquid distributor devices 26 therein. In this way theliquid that is to be evaporated streams downwards while being evaporatedthrough the heat exchanger stage L4 to the separating space [5-1 andfurther through L2 to E2 and from there through L3 to the separatingspace E3, from which the evaporated liquid is removed from the bottomofthe end cap 3 by means ofa pipe 28 and a pump 29. The steam is removedfrom the separating stage E3 through a pipe 30 into atube-surfacecondenser Pl.

The condensate of fresh steam is removed from the heat exchanger L-lthrough a pipe 32 and a pump 33. What is called secondary condensate isremoved from the condensing side of the heat exchanger L-2 along a pipe34 and it expands through a throttle means 35 to the condensing side ofthe heat exchanger L-3. The condensate from the unit L-3 is removedthrough the pipe 36 to an outlet pump 37 for secondary condensate. Tothe suction side of the pump has also been connected the condensate fromthe surface condenser Pl by means of a pipe 38. Hereby the surfacecondenser may be located as low down as the pressure difference betweenthe heat exchanger L3 and the lower tube plate of the surface condenserP-l allows. v

The removal of air from the heat exchanger Ll takes place through a pipe39 and through a throttle means in this pipe.

The removal of gas from the heat exchangers L-2 and L3 takes placethrough the pipes 40 and 41, respectively, and through throttle means inthem, 42 and 43 respectively. into the steam pipe 30, which leads to thesurface condenser P-l. The surface condenser P-l is fitted with asimilar subsequent separating cyclone for steam and with a dropseparator as described in connection with the heat exchangers L-2 andL-3. The liquid starting from the subsequent separating cyclone isconducted by means ofa pipe 44 into the pipe 28 and further to the pump29 for removal of the liquid.

The evaporation set. which consists of the heat exchangers L-l, L-2, L-3in this way connected together, stands on a foundation 45 consisting ofa prolongation of its own jacket I. The evaporator set can be locatedoutdoors and the surface condenser PI, for example, inside a building ona plane as indicated in FIG. 1. In FIG. I no. 46 describes a pipe forcooling water of the surface condenser P-1 and no. 47 a pipe for theremoval of warm water.

A pipe 48 leads the gases into a vacuum device, which is in the drawingdesignated with 49. The vacuum device may consist of any known vacuumdevice, for example. a vacuum pump, the pipe for whose gasket andcooling water is marked with 50.

In FIG. 2 L-I, L-2, L-3, L-4 and L-S illustrate heat exchangers of thedifferent stages in a five-stage evaporator unit. which heat exchangersare interconnected by means of a cylindrical jacket 1, whose top andbottom ends are fitted with end caps 2 and 3.

Into the jacket 1 pairs of tube plates 4-5, 6-7, 8-9, 39-40 and 4142have been arranged to which a number of tubes have been fastened so thatseparate heat exchangers LI, L-2, L3. L-4 and L-S, are formed and thatafter the lower tube plates 5, 7, 9, 40 and 42 pro-separating spaces El,E2, E3, E4, and E-5 are formed. The heights of the separating spaces E-2and E4 are hereby at least equal to the length of the tubes 10 used inthe heat exchangers.

The top sections of the heat exchangers are enclosed by steamdistributor jackets 13a and 13b. of which the jacket 13b in the heatexchangers L-2 to L-5, together with section 14b of jacket 1, the topsection of which is fitted with an opening and which is located insidethe steam distributor jacket 13b, forms a subsequent separator cyclonefor steam. The steam distributor jacket 13a in the heat exchanger L-lsimilarly, together with section 14a, forms a normal steam distributorwhich is open upwards and into which the primary steam is fed through apipe 3].

To the steam distributor jacket 13b of each heat exchanger L2, L-3, [f4and L-5 a steam pipe 15a, 15b, 15c and 15d starting out from theseparating space El E2, E3 and E4 of the respective preceding stage isconnected, and in the corresponding way an outlet pipe 16a, 16b, 16c and16d for separated liquid, fitted with a throttle means 17, goes out fromthe bottom edge of the steam distributor jacket.

Each tube 10 of each heat exchanger Lr-l to L-5 is at its top end fittedwith liquid distributor device 26, as was described in connection withFIG. 1. Underneath the tube plate at the bottom end of the heatexchanger units L4 to L-S there is, arranged in the separating space E-land ES, a conical separating plate system 27a, in which the lower coneis fitted with holes along its lower sphere. When the hot liquid-steammixture coming from the tubes 10 is tossed against the separating platesystem, the liquid is separated from the steam. Similarly, underneaththe tube plate at the bottom end of the heat exchanger units L-2, L-3and L-4 there is, arranged in the separating spaces E-2, E3 and E4, aconical separating plate system 2712, wherein the lower cone is closedalong its outer sphere. The main difference in respect of the embodimentaccording to FIG. 1 lies therein that the stages L-3, L-4 and L-5 haveno internal heat exchangers of the units and that the entire evaporatingdevice is, in respect of the liquid, divided into pre-evaporation andafter-evaporation stages.

The pre-evaporation stage consists of the heat exchangers L3, L4 and L-Sand the after-evaporation stage of the heat exchangers L-I and L-2. Theliquid that is to be evaporated is fed by means of a pump 25 into a pipe250 and distributed by means of the pipes 25!), 25c and 25d to theseparating spaces E2, E3 and E4 of the units L2, L3 and L-4 underneaththe separating plate systems 2712 therein. Since the feed liquor has ahigh temperature, the steam that has been formed by means of itsexpansion in the separating space E2, E3 and E4 passes between the conesof the separating plate system 2712 into the upper space and is combinedwith the steam from the preceding stage and passes through therespective steam pipes 15b, 15c and 15d into the heat exchangers L3, L-4and L-S, The liquid evaporated at the stages L-3, L4 and L-5 iscollected to a pump 29 by means of pipes 51 and 52, which start from thespace formed by the lower cone in the separating plate system 27b of thepre-separating stages E3 and E4, as well as through a pipe 28 from thebottom limited by the end cap 3. The pump 29 removes the pre-evaporatedliquid, for example, into an intermediate solution tank, to a spiritdistillery or directly to the after-evaporation. The pump 29 may consistof three separate pumps or of a multi-stage pump.

In other words, the liquid fed into a stage is only evaporated in thisstage and only the steam separated from it is used in the followingstage, whereby the liquid removed from each stage and collected receivesthe same final concentration as would have been achieved by feeding theentire feed liquid into stage L-3 and further downstream to L4 and L-S,but with a higher final temperature, without using internalafter-heaters arranged in the units or possible outer heat exchangers.The liquid that has expanded after being fed in, streams to the heatexchangers L3, L-4 and LS through the liquid distributor device 26 atthe top end of the tubes 10, which device guides the liquid into eachpipe in order to form a film on its inner surface. The steam from theseparating stage ES is removed through a pipe 30'into a tube-surfacecondenser P-l.

The liquid that is to be after-evaporated is fed either byv means of apump 29 or a pump 53 through a pipe 54 and a pipe 24 which passesthrough the interior heat exchangers 20, '21 arranged in the heatexchangers L2 and Ll and through the separating space E-l that connectsthese into the space limited by the end cap 2 at the top end of the heatexchanger L-l. The interior heat exchangers 20 and 21 constitute a partof the tube group of the heat exchangers L2 and LI, in which the topends of the evaporation tubes are fitted with a liquid distributordevice 26.

The liquid that has been evaporated in the stage Ll through the punchedseparating plate system 27a in the separating space E-l passes downwardsto the stage L-2 at the same time as the steam resulting from stage Llis guided by means of a steam pipe a into the steam distributor jacket13b of the stage L2. From the top side of theseparating system 27b inthe separating space E2 the steam departs through a pipe 15b into theheat exchanger'L3 at the same time as the evaporated liquid is removedfrom the space formed by the lower cone in the same separating platesystem 27b through a pipe 55 and by means ofa pump 56. The outlet pipel6a. going out from the subsequent separator cyclone of the stage L2,for separated liquid is connected'to the separating space E2 at thebottom side of the separating plate system 27b.

The condensate of fresh steam from the heat exchanger L-l is removedthrough a pipe 32 and a pump 33. The secondary condensate is removedfrom the condensate side of the heat exchanger L2 along a pipe 34 and itexpands through a throttle means 35 to the condensate side of theheat'exchanger L3.

Similarly the condensates of the units L3 and L4 are removed throughpipes 34aand 34b and through the throttle means 35a and 35b in thesepipes always to the condensate side of the following stage. Thesecondary condensate from stage LS departs through a pipe 36 to anoutlet pump 37 for secondary condensate. The

condensate from the surface condenser P-l is also conducted to thesuction side of this pump through a pipe 38.

The air removal from heat exchanger L-l takes place through a pipe 39and through a heat exchanger in it.

The removal of gas from the heat exchangers L2, L-3,'

- without pre-heating directly into the top end of the heat exchangerLl, whereby the interior heat exchangers and 21 in the heat exchangerstages L2 and Ll are omitted together with the collecting pipe 24. Inthe other respects the transmission of the liquid and the steam takesplace in the way described in connection with FIG. 2. The embodiment canbe further modified so that the feeding of the liquid to beafter-evaporated is distributed without preheating to the stages Ll andL2 by arranging a feeding branch from the pipe 54 to the bottom side ofthe separating plate system arranged in the pre-separating space 5-1. Atthe same time the separating plate system 27a is substituted for by aplate system 27b, in which the liquid evaporated from the space formedby the lower cone in the stage Ll is connected by means of a pipe to theliquid that comes through a pipe 55 from the space formed by the lowercone in the'separating plate system 27b in the preseparating space E2.Hereby the same situation is reached as in the pre-evaporation stage,i.e., the liquid fed into a stage is evaporated only in this stage andonly the steam separated from it is used in the following stage, wherebythe liquid removed from each stage and collected receives the same finalconcentration, but a higher temperature, without interior preorafterheaters, than by means of feeding all the liquid into stage Ll.Since the evaporated liquid that is to be removed is consequentlysuperheated, it is expanded in a separate expansion vessel between thepipe 55 and the pump 56. The steam separated in the vessel is conductedby means of a pipe into the steam pipe 15b leading into the stage L3,and the liquid is removed by means of the pump 56.

FIG. 5, which shows a modification of the embodiment according to FIG. 2is different mainly in the respect that the pre-evaporation stage, whichconsists of the stages L3, L4 and LS, and the after-evaporation stage,which consists of the stages Ll and L2, consist of separate tower-shapedevaporation units each standing on a fundament of its own, 45b and 45a,and that the primary steam unit Ll of the after-evaporation stage islocated lowest in the-set.

The secondary condensate is removed from the condensate side of the heatexchanger L2 through a pipe 57 and through a throttle device 58 in thepipe into an expansion vessel 59. The expansion steam is conducted fromthe expansion vessel through a pipe 600 to steam pipe 15b and through apipe 60b to steam pipe 15c and the expanded liquid through a pipe 61 topipe 34b.

In the FIGS. 1a and lb illustrate a cylindrical jacket which connectsthe different stages in each of the separate evaporation units, and 2a,2b and 3a, 3b illustrate the end caps arranged in their top and bottomends. The separating plate system in the separating space E2 after thestage L2 has been replaced by a removable section 62 that separates thestages L2 and L-l from each other. The liquid that is to beafter-evaporated is fed by means of pump 29 or pump 53a along the pipe54 and through a four way valve 63 along a pipe 65 to the upper end ofthe unit L-2 to the space limited by its end cap 2a or along a pipe 66to the upper end of the unit L-1 to the space separated by the section62. The liquid evaporated in the stage L2 departs from the separatingspace E2 from the bottom of the space 62 through a pipe 66a by means ofa pipe passing by the pump 67 and through the four way valves 68 and 63along a pipe 66 to the top end of the unit L-l or by means of the pump67 through the four way valve 68 and a pipe 69. The evaporated liquidfrom stage Ll is removed from the bottom of the space 62 of theseparating space El by means of a pipe 71 and a pump 72 through thevalve 68 and the pipe 69 or through the four way valves 68 and 63 andthe pipe 65 to the top end of the unit L-2. By means of the four wayvalves and the pipes combining them the units L-l and L2 can, ifnecessary, be exchanged with each other so that each of them comes towork alternatively as the strong liquid unit, whereby after exchange themore diluted liquid washes the unit that has worked as the strong liquidunit, and the evaporation takes place alternatively as upstreamevaporation and alternatively as downstream evaporation. The outlet pipel6a, coming from the subsequent separator cyclone of the stage [1-2, forseparated liquid is connected to the separating space E-2.

In the other respects the embodiment according to FIG. 5 corresponds tothe description given above.

FIG. 6 shows a modification of the embodiment according to FIG. 2 inrespect of the steam distributor section in the stages L-3 and L-4.

The embodiment differs from what is shown in FIG. 2 mainly in therespect that the outer steam pipe 150, which in FIG. 2 connects theseparating space E-3 of the stage L-3 with the stage L-4, and theseparating plate system 27b in the separating space E3 have beensubstituted for by an annular pipe channel 76 limited between the jacket1 and the inner steam distributor jacket 13b, which channel connects thepre-separating space E3 to the stage L4, and together with aprolongation 14b fitted with openings at the top end of the steamdistributor jacket 13b, forms a subsequent steam separator cyclone, aswell as a collecting cone 73 fastened to the hole plate 9 of the stageL-3 and a distributor pipe 74 which forms a prolongation of thecollecting cone 73 and projects into the pre-separating space E-3limited by the steam distributor jacket 13b and the tube plate 39 of thestage L-4. The bottom end'of the distributor pipe 74 is closed and thejacket is fitted with openings.

The upper tube plate 39 of the stage L4 is fastened to the prolongation14b of the steam distributor jacket 13b. and the upper end of the steamdistributor jacket 13b is fitted with steering blades 75 adjoining thecover 1 and steering the steam streaming as a rotating movement down inthe annular pipe channel 76.

The liquid separated on the bottom of the subsequent separator cycloneis removed by means of a pipe 16c, which is fitted with a throttle means17, into a distributor pipe 74. In respect ofthe other stages the abovediscription is applicable.

By means of an embodiment according to FIG. 6 uniform, towerlikeconstruction limited by the jacket 1 is obtained.

FlG. 7 illustrates an embodiment in which the steam flow in each heatexchanger is arranged to take place in a direction opposite to thedirection of the liquid flow. Corresponding parts have been providedwith the same numerals as in the preceding embodiments.

The embodiment according to FIG. 7 differs from the embodiment accordingto FlG. 6 in that an annular tubular channel 76 is provided between thecylindrical jacket I and the internal steam distributor jacket 1311.This channel 76 connects the pre-separating space E-4 with the heatexchanger L3 and forms together with the upper extension 1412 of thejacket 13h a subsequent steam separating cyclon. The channel 76 formstogether with a collecting cone 73 fastened to the tube plate 8 of theheat exchanger L,3, a distributor pipe 74 extending into thepre-separating space E-3, a central pipe 73a fastened to the tube plates8 and 9 and a collecting cone 73b fastened to the tube plate 9, a liquidcirculation system for guiding liquid to be evaporated from thecollecting cone 73 through the central pipe 73a and the collecting cone73b to the heating tubes 10 and further from said tubes through thespace 73(' formed between the collecting cone 73 and the jacket 1 to thedistributor pipe and further to the preseparating space E- 3. Liquid isfed into the system from the pipe 54 and the evaporated liquid is fedfrom the stage L-3 by means of the pipe 66/) to the stage L4 and furtherfrom the stage L-4 by means of the pipe 71!) to the stage L-S.

The lower tube plate 9 of the heat exchanger L-3 is fastened to thejacket 1 by means of guiding blades 75 which cause the steam to flow ina spiral upwards in the channel 76. The liquid separated in thesubsequent separating cyclone formed by the channel 76 flows backdirectly to the collecting cone 73.

The invention is not restricted to the above embodiments, presented asexamples, but it also relates to evaporation devices fitted with someknown vertical tube heat exchanger that can be modified within theframework of the patent claims. The embodiments according to the presentinvention are particularly advantageous if tube heat exchangers fittedwith double tubes, for example according to the Swedish Pat. No.320,991, are used.

What 1 claim is:

1. A device for evaporating liquids comprising a plurality of evaporatorunits connected in series, each of said evaporator units having a heatexchanger section with vertical heat exchanger tubes having open endsarranged therein and a vapor-liquid separating section downstream ofsaid heat exchanger section, at least two of said evaporator units beingvertical and stacked on top of one another, the heat exchanger sectionin the first evaporator unit having a steam distributor section andmeans for admitting steam therein, each of the other heat exchangersections having a vapor distributor section comprising a liquidseparating cyclone for separating liquid from incoming vapor, and meansfor tangentially introducing separated vapor to each ofsaid vapordistributor sections from one of said vapor-liquid separating sectionsand for tangentially introducing said separated vapor into said vapordistributor section to separate liquid therefrom.

2. The device of claim 1 in which the evaporator units have a commonjacket and in which the evaporator units form a continuous tower-likeunit.

3. The device of claim 1 and further comprising means for transportingseparated liquid from at least one of said vapor distributor sections tothe vaporliquid separating section of the succeeding evaporator unit.

4. The device of claim 1 in which said liquid separating cycloneincludes a drop separator for separating liquid from incoming vapor.

5. The device of claim 1 in which the vapor distributor section includesa jacket wall surrounding the vertical heat exchanger tubes and havingat least one hole therein below the separated vapor inlet for regulatingthe separated liquid level.

6. The device of claim 1 in which the height of at least every othervapor-liquid separating section is at 9 least equal to the length of thevertical heat exchanger tubes used inthe evaporator units.

7. The device of claim 1 in which the openings in the vertical heatexchanger tubes in adjacent evaporator units are aligned and in whichthe heat exchanger sections have end plates which are adapted to beclosed by means of a cover.

8. The device ofclaim l in which the means for trans porting theseparated vapor to the vapor distributor section from the vapor-liquidseparating section is arranged to transport the vapor in a directionopposite to the direction of liquid flow.

9. The device of claim 1 in which the means for transporting vapor tothe vapor distributor section from the vapor-liquid separating sectionis arranged to transport the vapor in the same direction as thedirection of liquid flow.

10. The device of claim 1 and further including means for simultaneouslytransporting feed liquid to at least two separate evaporator unitsarranged so that the feed liquid is evaporated only in the evaporatorunit into which it is introduced and further comprising means forcombining the separated liquid removed from each of the vapor-liquidseparating sections of said evaporator units.

11. The device of claim 10 and further including means for transportingthe separated vapor from said vapor-liquid separating sections to thesucceeding evaporator unit.

12. The device of claim 1 in which at least one of said evaporator unitsincludes a heat exchanger for preheating the feed liquid before it isintroduced into said vertical heat exchange tubes.

13. The device of claim 1 in which said vaporliquid separating zonesincludes a separating plate having openings therein for separating andremoving liquid.

14. The device of claim 1 in which said liquid separating cycloneincludes steering blades for effecting said tangential movement of saidseparated vapor.

1. A device for evaporating liquids comprising a plurality of evaporatorunits connected in series, each of said evaporator units having a heatexchanger section with vertical heat exchanger tubes having open endsarranged therein and a vaporliquid separating section downstream of saidheat exchanger section, at least two of said evaporator units beingvertical and stacked on top of one another, the heat exchanger sectionin the first evaporator unit having a steam distributor section andmeans for admitting steam therein, each of the other heat exchangersections having a vapor distributor section comprising a liquidseparating cyclone for separating liquid from incoming vapor, and meansfor tangentially introducing separated vapor to each of said vapordistributor sections from one of said vaporliquid separating sectionsand for tangentially introducing said separated vapor into said vapordistributor section to separate liquid therefrom.
 2. The device of claim1 in which the evaporator units have a common jacket and in which theevaporator units form a continuous tower-like unit.
 3. The device ofclaim 1 and further comprising means for transporting separated liquidfrom at least one of said vapor distributor sections to the vapor-liquidseparating section of the succeeding evaporator unit.
 4. The device ofclaim 1 in which said liquid separating cyclone includes a dropseparator for separating liquid from incoming vapor.
 5. The device ofclaim 1 in which the vapor distributor section includes a jacket wallsurrounding the vertical heat exchanger tubes and having at least onehole therein below the separated vapor inlet for regulating theseparated liquid level.
 6. The device of claim 1 in which the height ofat least every other vapor-liquid separating section is at least equalto the length of the vertical heat exchanger tubes used in theevaporator units.
 7. The device of claim 1 in which the openings in thevertical heat exchanger tubes in adjacent evaporator units are alignedand in which the heat exchanger sections have end plates which areadapted to be closed by means of a cover.
 8. The device of claim 1 inwhich the means for transporting the separated vapor to the vapordistributor section from the vapor-liquid separating section is arrangedto transport the vapor in a direction opposite to the direction ofliquid flow.
 9. The device of claim 1 in which the means fortransporting vapor to the vapor distributor section from thevapor-liquid separating section is arranged to transport the vapor inthe same direction as the direction of liquid flow.
 10. The device ofclaim 1 and further including means for simultaneously transporting feedliquid to at least two separate evaporator units arranged so that thefeed liquid is evaporated only in the evaporator unit into which it isintroduced and further comprising means for combining the separatedliquid removed from each of the vapor-liquid separating sections of saidevaporator units.
 11. The device of claim 10 and further including meansfor transporting the separated vapor from said vapor-liquid separatingsections to the succeeding evaporator unit.
 12. The device of claim 1 inwhich at least one of said evaporator units includes a heat exchangerfor preheating the feed liquid before it is introduced into saidvertical heat exchange tubes.
 13. The device of claim 1 in which saidvaporliquid separating zones includes a separating plate having openingstherein for separating and removing liquid.
 14. The device of claim 1 inwhich said liquid separating cyclone includes steering blades foreffecting said tangential movement of said separated vapor.